Auxin: Auxin is a phytohormone. The bio-chemical substances formed in the plant bodies which, remaining in a very lower concentration; control the growth of plants is known as phytohormone.

Formation and Nature: The word auxin is derived from the Greek word auxein meaning to grow. At appropriate concentrations of auxins normally stimulate the enlargement of cells and increase the flexibility of cell walls. Auxin is a growth stimulating hormone. The main function of auxin is to help plants grow. Auxin stimulates plant cells to elongate, and the apical meristem of a plant is one of the main places that auxin is produced. This makes sense because the apical meristem is also the location that all the other parts of a plant grow from – the stem, leaves, and flowers.

Types: The main auxin of plants is Iodole -3 acetic acid (IAA).

Position: Auxin is mostly present at a real amount in the growth regions, such as- apical bud. Indole-3 acetic acid (IAA) is formed in the plant bodies from tryptophan.